hdu 5343 MZL's Circle Zhou（后缀自动机）

题目链接：hdu 5343 MZL’s Circle Zhou

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
typedef unsigned long long ll;
const int maxn = 90005;
const int SIGMA_SIZE = 26;

struct SAM {
    int sz, last;
    int g[maxn<<1][SIGMA_SIZE], pre[maxn<<1], step[maxn<<1];
    int pos[maxn<<1];
    ll tot, right[maxn<<1], cnt[maxn<<1], dp[maxn<<1];

    void newNode(int s) {
        step[++sz] = s;
        pre[sz] = 0;
        memset(g[sz], 0, sizeof(g[sz]));
    }

    int idx(char ch) { return ch -'a'; }

    void init() {
        tot = 0;
        sz = 0, last = 1;
        newNode(0);
    }

    void insert(char ch);
    void get_tuopu();
    void get_right(char* str);

    ll solve(ll* c);
    void presolve(ll* c);
}SA, SB;

char a[maxn], b[maxn];

int main () {
    int cas;
    scanf("%d", &cas);
    while (cas--) {
        scanf("%s%s", a, b);
        int na = strlen(a); SA.init();
        for (int i = 0; i < na; i++) SA.insert(a[i]);
        int nb = strlen(b); SB.init();
        for (int i = nb-1; i >= 0; i--) SB.insert(b[i]);

        ll c[30];
        memset(c, 0, sizeof(c));
        SB.presolve(c);
        printf("%llu\n", SA.solve(c));
    }
    return 0;
}

void SAM::presolve(ll* c) {
    get_tuopu();
    memset(dp, 0, sizeof(dp));
    dp[1] = 1;

    for (int i = 1; i <= sz; i++) {
        int u = pos[i];
        for (int j = 0; j < SIGMA_SIZE; j++) {
            int v = g[u][j];
            if (v == 0) continue;
            c[j] += dp[u];
            dp[v] += dp[u];
        }
    }
}

ll SAM::solve(ll* c) {
    get_tuopu();

    memset(dp, 0, sizeof(dp));
    dp[1] = 1;

    ll ret = 0;
    for (int i = 1; i <= sz; i++) {
        int u = pos[i];
        for (int j = 0; j < SIGMA_SIZE; j++) {
            int v = g[u][j];
            if (v == 0) ret += dp[u] * c[j];
            else dp[v] += dp[u];
        }
        ret += dp[u];
    }
    return ret;
}

void SAM::insert(char ch) {
    newNode(step[last] + 1);
    int v = idx(ch), p = last, np = sz;

    while (p && !g[p][v]) {
        g[p][v] = np;
        p = pre[p];
    }

    if (p) {
        int q = g[p][v];
        if (step[q] == step[p] + 1)
            pre[np] = q;
        else {
            newNode(step[p] + 1);
            int nq = sz;
            for (int j = 0; j < SIGMA_SIZE; j++) g[nq][j] = g[q][j];

            pre[nq] = pre[q];
            pre[np] = pre[q] = nq;

            while (p && g[p][v] == q) {
                g[p][v] = nq;
                p = pre[p];
            }
        }
    } else
        pre[np] = 1;

    tot += step[np] - step[pre[np]];
    last = np;
}

void SAM::get_tuopu() {
    for (int i = 0; i <= sz; i++) cnt[i] = 0;
    for (int i = 1; i <= sz; i++) cnt[step[i]]++;
    for (int i = 1; i <= sz; i++) cnt[i] += cnt[i-1];
    for (int i = 1; i <= sz; i++) pos[cnt[step[i]]--] = i; 
}

void SAM::get_right(char* str) {
    int p = 1, n = strlen(str);
    for (int i = 0; i <= sz; i++) right[i] = 0;

    for (int i = 0; i < n; i++) {
        int v = idx(str[i]);
        p = g[p][v];
        right[p]++;
    }

    for (int i = sz; i; i--) {
        int u = pos[i];
        right[pre[u]] += right[u];
    }
}